This procedure is defined in the server but not documented via ad_proc or proc_doc and may be intended as a private interface.
The procedure is defined as:
proc dom::Encode {value} {
array set Entity {
$ $
< <
> >
& &
\" "
' '
}
regsub -all -- {([$<>&"'])} $value {$Entity(\1)} value
return [subst -nocommand -nobackslash $value]
}